The use of an aligned fiber sheet impregnated with curable resin is a well-established technique to form articles with high strength to weight ratios. Stress skin articles formed through the use of an aligned fiber sheet impregnated with curable resin illustratively include boat hulls, vehicle body panels, aircraft components, missile components, surfboards, prosthetics, and the like. Unfortunately, combinations of aligned fibers with conventional monomers and resins cross linking to form thermoset polymers have failed to afford a package of completely desirable properties. Prototypical of such aligned fiber sheet systems is fiberglass impregnated with curable epoxy resins. Limitations in the use of such articles are article performance and production techniques.
The incomplete ability of resin to wet a fiber leads to reduced pull out energy from the fiber from a cured resin matrix resulting in lower article strength. As curable resins are most often hydrophobic, silanization or other modification of glass fibers is accomplished to render the glass hydrophobic. While this is costly, it is effective to increase article strength; however, many fiber materials are either damaged or otherwise not amenable to surface modification to change fiber surface energies. High strength fibers such as carbon and aramid are representative of fibers that are comprised by certain surface treatments. Existing resins also suffer from erratic cure profiles, susceptibility of cure to ambient moisture and light, and article yellowing after cure upon exposure to sunlight.
The toxicity, odor, and other negative handling attributes of resins have also limited the application for aligned fiber containing cured matrix articles. As an ever increasing number of resins are found to have toxicity even in cured articles, the applications have accordingly diminished for fiber containing cured matrix materials. Additionally, the increased requirements on curing environment, worker safety and ventilation further limit the locations of usage. This has had a particularly large impact on field repair of articles.
Thus, there exists a need for an oriented fiber reinforced thermoset material having improved performance, handling, and weatherability relative to conventional resins.